The Lychee (Litchi chinensis) and its relatives are highly regarded exotic fruits. The lychee is extensively grown in the sub-tropical south east Asia, where it seems to have been cultivated for well over a thousand years. While the main country of origin seems to have been China, in recent years it has been cultivated and grown, both for domestic use and export, in a number of additional countries, including Israel, South Africa and Thialand.
Lychees are a very palatable fruit and are highly regarded as a dessert, either in the form of the fruit itself as such, or as a major component in various combinations.
Lychees are usually harvested in the early summer, and can be kept at usual room temperatures without spoiling for only about 1-3 days. Under refrigeration, usually in the vicinity of 10.degree. C., untreated lychee can be kept a bit longer, for a few weeks. The color of the usual varieties of the ripe lychee (pericarp-shell) upon harvesting is reddish, usually delicate rose pink to bright strawberry-red. At ordinary room temperatures, this quickly turns to brown, often within 24 hours after harvest. Over the years, major efforts have been devoted to developing methods and conditions for extending the relatively short period of post harvest product quality and shelf lifetime, with a major emphasis on maintaining the fresh attractive color of the pericarp. The various methods that have been developed for this purpose over the years involve, refrigeration, plastic wrapping, transport in ice water and treatment with sulfur or sulfur compounds, such as, SO.sub.2.
In recent years, the awareness and concern about toxic chemical residues in various agricultural and food products, have become a major public agenda item worldwide. The issue has become particularly acute in developed consumer countries, where ever increasing and prohibiting legislation is continually restricting the use of chemicals and treatments that until now have played a major role in food pest control and food stuff protection from spoilage.
For example, in recent years, it has become a common practice to treat lychee with sulfur to prevent spoilage and deterioration. This includes preventing any deterioration in the reddish pericarp color. There are now many countries, including the United States, that prohibit the import of agricultural products and food stuffs treated with sulfur. Furthermore, even when the use of certain sulfur compounds such as SO.sub.2 to treat agricultural products and food stuff is allowed, there are regulations that require that this be explicitly stated on the packaging. As a result, environmentally and health concerned consumers are discouraged from purchasing such products.
Consequently, the need for an environmentally and consumer friendly process, based exclusively on food grade acceptable substances, for treating lichee to extend the relatively short period of post harvest product quality and shelf lifetime, is obvious. Such a process that extends the product quality lifetime sufficiently to allow the product to be transported to consumer markets by conventional surface transportation means rather than by expensive air transport, would be particularly desirable.
It is therefore an object of certain aspects of the present invention to provide an improved, convenient, environmentally compatible process for preserving the product quality of lychee fruit, particularly the pericarp color.
It is a further object of certain aspects of the present invention to provide such a process that will extend the product quality and post harvest shelf lifetime sufficiently, so as to allow the use of common surface transportation means to transport the lychee fruit to distant consumer markets.
It is yet a further object of certain aspects of the present invention to provide such a process that is based on relatively simple, readily available, food grade substances.
It is yet a further object of certain aspects of the present invention to provide such a process that is relatively simple to implement.